AbstractCompartment syndrome (CS) is an emergency condition caused by muscle necrosis that can lead to locomotor dysfunctions. Intra-fascial bleeding of a limb due to direct trauma, reduction of fractures, or tight casting or bandages may cause acute CS. Although acute CS has many causes, few cases of spontaneous CS have been reported in the literature without any apparent reasons. We present a case of a 53-year-old male who had a spontaneous CS in his right forearm. There was no any evidence of acute major or minor repetitive trauma. He had a history of taking multiple anticoagulants due to previous femoral artery repair and still uses anticoagulants. After evaluation, we performed fasciotomy and removed an organized hematoma between the deep and superficial flexor tendons. The patient has recovered completely without any relapse at the 2-year follow-up. Detailed information should be given to patients who are taking anticoagulants about acute CS.